Framer,
I would consider a +20 degs temperature change an event comparable to encountering severe clear air turbulence, and would start an emergency descent. I don't plan my flight on the odd occasion that might happen every 50.000 flight. Though I know that you have a more extreme environment down under. I mean when a jellyfish can kill you...
You wrote the you were even below the optimum and only just managed to maintain altitude. I assume that is was more a coincidence that you were below optimum... hence had you been higher you would have had to descent too?
Therefore, it would be very inefficient always to fly with the worst possible scenario in mind. As an extreme example, then we could stay below 10000 feet too, to be on the safe side in case of a rapid decompression.
That is exactly what I mean, we can't continue to add personal margins on established margins... where will it end? ...that we stay on the ground.
Boeing say it is safe to operate the aircraft at max altitude, so that is what I am doing (with the use of common sense as pointed out previously).
I have no problem adding margins to margins, when it is justified. I happily bring 2 tons extra fuel if there is a reason to do so. But I also fly with min required if there is no reason to bring extra. What I do not agree with is people saying "I don't fly with less than 800 kg extra", "I always want to see +800 feet on the max altitude before I climb" etc. I have only a big WHY? to say to that.
I put it to you that there is no margin when at Max altitude as you are already at a limitation of 100fpm capability and any degradation of performance puts you outside of that requirement.
Aha, there we have the misunderstanding!! You are confusing FMC max altitude with "service ceiling". This is absolutely incorrect. Flying at max FMC altitude is not flying at service ceiling. Because Boeing already build in a margin for you:
Optimum/Maximum Altitude (OPT/MAX)
Also displays the maximum possible altitude based on the selected target speed and the specified maneuver margin.
Values are advisory only. They are provided for crew reference.
So I guess I don't have to answer your question, as it is irrelevant.
As for the flaps up amber band, it doesn't say anything about thrust available vs. thrust required. Hence, with a decreasing speed approaching the top of the amber band it would be a good idea to select CON to have the extra thrust available (if you didn't already do so, routinely, as
pr. Boeing recommendation). If the speed continues to show a decreasing trend and getting close, a slight (to ATC unnoticeable) descent may help you out, as pointed out earlier.
Just to point out, despite my "dangerous" operating of the aircraft I was never in the low speed band. Except briefly one time, flying well below max altitude and flying through the edge of a CB with moderate turbulence. Lost about 300 feet altitude in the process with autopilot in CWS.
De facto,
Sorry, with you I really can't keep my eye on the ball anymore. You really have no clue, do you? Clacker for exceeding maximum maneuver speed?
Maybe Boeing should have added:
Flight crews intending to operate at or near the maximum operating altitude should be familiar with the performance characteristics, instrumentation, limitation and basic priciples of how airplane works in these and any other conditions. Flight crews should be certified and have been tested in their knowledge prior to operating the aircraft
Been a captain for 9 years? Complacency setting in already. I can almost hear it: "...I have always done so...."
Of curiosity what is a cost index 55 airline? Actually the cost index was 4 on the OFP, what does that then say about my airline?
As we were late and I wanted to bring the aircraft back on time for the next crew to have the min required turn-around time available I had changed the cost index 55, which is equal to LRC. The benefit is that the climb and descent speeds are changed too. For me it is more efficient to change one entry, than having to modify climb and descent pages manually too.
